Flexible magnetic disks now in use in word processing and personal computer applications are usually contained in a flexible jacket formed with an approximately rectangular opening as a head access window and also with a center opening for engagement of the disk with the disk drive. It is possible for dust or foreign matter to enter the flexible plastic jacket containing the magnetic recording disk through these openings and be deposited on the recording medium. Also, when such diskettes are held by the fingers at the head access opening, fingerprints can be formed on the surface of the recording medium. The magnetic recording medium is also exposed to mechanical damage through the head access window. On recording media disks with high information density, dust, fingerprints or mechanical damage can be serious problems causing dropouts to occur in signals reproduced from the magnetic recording medium. Therefore, it has been necessary to handle diskettes with great care.
There is currently a trend toward making recording media smaller in size (i.e., 3-4 inch diameter disks as opposed to the 51/4 and 8 inch diameter disks currently in use). The smaller diskettes have the advantage that they are very easily transported, even in a shirt or coat pocket. However, this advantage may lead to increased exposure to contaminants. The smaller size diskettes, because of their convenience, may be used in a broad range of applications ranging from computer terminals in factories to home computers.
The opportunity for the occurrence of the above-described types of damage should be minimized. There are existing designs to provide protection to diskettes. In general, these provide a case which is more rigid or durable than the traditional floppy disk cases, and they provide a shutter to keep dust and foreign matter from entering the case through the head access windows. Like the previously known diskettes, the newer versions usually provide wiping fabric or cleaning sheets often made of non-woven material adhered to the inside of both halves of the jacket or cartridge to wipe any debris from the recording medium disk as it rotates.
The use of a shutter mechanism allows the head access windows to be open when the diskette is loaded into a disk drive, and to be covered when the assembly is not in a drive, thus preventing fingers from touching the recording medium. There are several shutter designs in the patent literature, and usually the shutter is actuated by a spring which keeps it in the closed position when not in use. When the diskette is inserted into a drive, the shutter in some designs is automatically opened by some external force, such as by engagement of a shutter actuating tab with a part of the disk drive housing. One such design has a compression spring located in the edge of the cartridge where it is engaged by a tang on a sliding shutter. In this particular location, a substantial portion of the total length of the compression spring is exposed to dirt and dust.
Prior art three to four inch diameter diskettes have a wiping fabric which is in an annular shape, having a space cut out of the annulus for the head access hole. One problem related to the wiping fabric which can occur is the formation of protrusions or stringers of the wiping fabric into the head access hole. These stringers can come between the recording medium and the recording or read head, interfering with the record or playback process.